Electric blanket



R. F. sHAw 2,948,802

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ROBERT F. SHAW of i -fmd @wf United States Patent Office Patented Aug. 9, 1960 ELECTRIC BLANKET Robert F. Shaw, Davenport, Iowa, assignor to the United States of America as represented by the Secretary of the Army Filed May 5', '1958, Ser. No. 733,217

2 Claims. (Cl. 219-46) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to an electrically heated blanket, or the like, and more particularly to a water repellent, thermally insulated electric blanket.

1 Prior art blankets of the kind to which the present invention is directed, although satisfactory for certain applications, have been found to perform poorly for other applications, particularly in cases of extreme temperature and adverse weather environments. Analysis shows that such poor performance is, for the most part, due to selection of materials as well as structure. For example, under extreme temperature conditions, certain requirements are that the materials stand up under ternperatures as low as -65 degrees F., and as high as 158 degrees F. Under such cold temperatures, many materials become stiff and hence brittle thereby breaking easily and destroying the insulating characteristics of the material. In addition thereto, it is customary to stitch the layers of material in quilted fashion or to perforate the layers with buttons or fasteners in order to preserve the several layers of the blanket in their proper original relationship thereby to prevent bunching of the inner layers within the outside covering. Stitching or perforating the blanket layers is objectionable from the standpoint that each of the perforations allows moisture to enter the interior of the blanket which, over a period of time, interferes with the electrical operation and efficiency of the blanket. In addition thereto there is ever present the objectionable results of piercing the insulation or breaking the heating wires as a consequence of the stitching operation. In many cases where this happens, the blanket is so defective that it is useless.

Accordingly, it is a primary object of the present invention -to provide an electrically heated blanket which will overcome the above mentioned disadvantages.

It is another object of the present invention to provide an improved structure for electrically heated blankets, or the like, which will preserve the operating characteristics throughout extreme environmental conditions. A further object of the present invention is to enhance the moistureproof quality of an electrically heated blanket. Still another object is to provide an electrically heated blanket having greatly improved eiciency.

It is also an object to provide a moistureproof, electrically heated blanket which will preserve substantially the form in which it was made originally.

Still further it is an object of the present invention to provide an electrically heated blanket the heating components of which :are completely sealed against ambient atmospheric conditions.

Also it is an object of the present invention to provide an improved structure for electrically heated blankets, or the like, which will make it less vulnerable to the difficulties occasioned by stitching or quilting.

An additional object of the present invention is to provide an electrically heated blanket which is simple and easy to construct and yet highly efficient in use.

In accordance with the electrically heated blanket of the present invention, the insulating layer of material has the heating means adhesively secured to one side thereof and the whole is adhesively secured to and encompassed by an elastomeric coated material which will seal the parts against ingress of moisture and other ambient atmospheric conditions.

The novel features characteristic of the present invention, as well as additional objects and advantages thereof, will be understood better from the following detailed description when read in connection with the accompanying drawings in which:

Figure l is a perspective view of an electrically heated blanket in accordance with a preferred embodiment of the present invention;

Figure 2 is an enlarged fragmentary view in perspective of the blanket shown in Figure l;

Figure 3 is a fragmentary view, similar to Figure 2, of a second embodiment of the present invention;

Figure 4 is a fragmentary view, similar to Figure 2, of a third embodiment of the present invention;

Figure 5 is an exploded View of the components employed in blankets according to the present invention, and in particular those components embodied in the species shown in Figures 1 and 2;

Figure 6 is an enlarged fragmentary view of the elastomeric cover material;

Figure 7 is an exploded view of a fourth embodiment of the present invention; and

Figure 8 is an enlarged fragmentary View of the radiation barrier material.

Referring more particularly to the drawings, wherein similar reference characters are used to designate corresponding parts, there is illustrated four embodiments of an electrically heated blanket in accordance with the present invention. Each of these embodiments comprises, generally, -a layer of insulating material 1, a heating means 3, and a cover 5.

The layer of insulating material 1 found to be excellent because of its moisture-resistant qualities comprises an expanded unicellular or closed cellular material of the type manufactured by United States Rubber Company under the trade name Ensolite Type l, or any equivalent thereof. This material is a polyvinyl chloride compound composed of a multiplicity of tiny spherical nitrogen gasiilled cells. The characteristics of this material are excellent thermal insulation, light weight, flexibility, and negligible moisture-absorption. Due to its unicellular structure, moisture-absorption is kept to a minimum thereby preventing formation of ice at extremely low temperatures with consequent reduction in insulating qualities as well as preventing promotion of corrosion of metal surfaces. These characteristics are particularly desirable for an electrically heated blanket which is intended for use under adverse weather conditions where equipment is subject to temperature extremes and precipitation.

The heating means 3 is disposed on one side of the insulating layer and comprises any suitable type of electrical resistance element capable of producing heat upon application of a source of electricity thereto. It has been found that a silicone rubber insulated heating wire 7 is entirely satisfactory for the purpose. The length of this wire and its particular arrangement will, of course, depend upon the design of the blanket and the heating requirements it is to serve. The wire is conveniently attached to the insulating layer by any suitable means which will preserve the original arrangement. Although the attaching of the wire is a matter of choice, it is suggested that the wire be attached to the insulating layer by an adhesive or, as particularly shown in Figure 5 of the drawings, it may be interwoven in a layer of insulating material or a fabric of nylon 9. In the latter case, the fabric wire carrier is secured to the insulating layer by an adhesive 11 to prevent displacement of the heating means within the covering.

The heating means or wire assemblyl 3 and the layer of insulating material 1 are disposed within a sealed compartment provided by a waterproof cover or fabric 5. Although the cover may be fabricated from any suitable material, it has been found entirely satisfactory to use an elastomeric covered material such as nylon cloth 13 coated on both sides with neoprene 15. The cover is adhesively secured to the wire :assembly and the insulation respectively so as to preserve the original arrangement of the components.

The cover is susceptible to application in at least three ways which will preserve the moistureproof characteristics by providing a seal or complete inclosure for the heating and insulating components. As a first, preferred embodiment, a moistureproof layer of cover material is disposed above and beneath the insulating layer and the heating means, and the open edges 17, 19 are disposed juxtaposed. The juxtaposed edges are adhesively bonded and folded together in an interlocking fashion after which they :are stitched intermediate the fold area thereby providing an impervious inclosure. As particularly shown in Figure 2 of the drawings, the stitching 21 is disposed intermediate the folds, that is, along the juxtaposed edges and spaced from the closed interior of the cover in order to preserve the seal provided by bonding the edges together inwardly of the stitched area. In addition a waterproof material may then be coated or sprayed over the stitched area. v

In a second embodiment, the open edges 23 are adhesively bonded together face-to-face and no stitching is applied. In this case, the bonding of the material is relied upon solely to effect the necessary seal.

In the third embodiment the open edges 25 are bonded together as in the second embodiment but stitching 27 is employed along the bonded edges to prevent separation thereof.

In addition to the three basic components of an insulating layer 1, a heating means 3 and a cover 5 employed in the first three embodiments, a fourth embodiment, shown in Figure 7, proposes the use of a radi-ation barrier 26 located on that side of the insulating layer opposite that on which the heating means is disposed and between the insulating layer and the cover. The barrier material should comprise a flexible layer of waterproof material which will effectively function to olfer resistance to heat radiation from within the blanket during periods of relatively cold ambient conditions and to oifer resistance to heat from the outside of the blanket during periods of relatively hot ambient conditions. A material or" this type which is found particularly suitable comprises a layer of foil 2-, such as aluminum foil, backed up with a layer of cotton scrim 30 which is adhesively .applied thereto. T he purpose of the cotton scrim backing is to prevent tearing of the aluminum foil.

In all embodiments, it is proposed that the blanket ,components be adhesively bonded together. Although this requirement can be satisfied by a layer of suitable adhesive which is applied entirely over the surfaces of the respective components, this type of construction is not the most desirable because the adhesive has a tendency to stiffen and hence interfere with the flexibility of the blanket. Therefore, it is preferred that the adhesive be promiscuously spotted on the components suiciently 4 to hold them in their original relation to each other and in this way interference with flexibility will be minimized.

In all embodiments, suitable means need be provided for connecting the heating component with a source of electricity (not shown). For this purpose, the cover is designed to accommodate a line cord 29 with plug 31 attached which extends through the cover material and is connected with the heating means 3.

From the foregoing, it will become obvious to those persons skilled in the lart that the electric blanketof the present invention will result in an improved moistureresistant product which is an excellent replacement for quilting. Because of its simplified structure, the blanket is readily adapted to simplified manufacturing techniques, and it is very light Weight `and easy to handle.

Although there is shown and described several embodiments of the present invention, it will also be recognized by persons skilled in the art that changes and modifications are possible within the spirit of the invention and within the scope of the appended claims. Therefore, it is desired that the embodiments shown and described herein shall be considered as illustrative and not as limit- What is claimed is:

1. An electrically heated blanket comprising at least one layer of expanded, closed cellular, insulating material and heating means attached on one side of said layer, a cover therefor comprising a moistureproof fabric encom passing said insulating layer and said heating means, said `fabric being adhesively attached respectively to said insulating layer and said heating means, juxtaposed edges thereof being disposed interlocked and folded, said edges being adhesively secured together to provide a sealed cinclosure for said insulating layer and said heating means, and stitching being disposed along said edges spaced from the closed interior of said cover in a manner to' provide a sealed portion of said fabric between said stitching and said closed interior.

2. An electrically heated cover comprising at least one layer of expanded, closed cellular thermal insulating material, electrical heating means attached on one side of said material, and a moistureproof cover therefor, said cover surrounding said material layer and said heating means and being adhesively attached respectively thereto, said cover having juxtaposed edges thereof being interlocked and folded and being adhesively attached to provide an impervious inclosure, the folds thereof being stitched along a line within the folded portion, and said heating means being extended through said cover for connection with a source of electrical energy.

References Cited in the file of this patent UNITED STATES PATENTS 2,548,468 Crise Apr. 10, 1951 2,612,585 McCann Sept. 30, 1952 2,617,011 MacKendrick Nov. 4, 1952 2,617,916 Neidnig Nov. 11, 1952 2,643,320 Pfenninger June 23, 1953 2,666,839 Boetel Ian. 19, 1954 2,698,893' Ballard Ian. 4, 1955 2,715,674 Abbott etal Aug. 16, 1955 2,735,926 Langlois Feb. 21, 1956 2,741,692 Luke Apr. 10, 1956 2,783,358 Wolf Feb. 26, 1957 2,802,091 MacKendrick Aug. 6, 1957 2,845,519 Willat July 29, 1958 2,873,352 Franco Feb. 10, 1959 

